Ingrid C. Burke

Yale University | YU · School of Forestry and Environmental Studies

In a 10-year study, we assessed the influence of five carbon (C) treatments on the labile C and nitrogen (N) pools of historically N-enriched plots on the Shortgrass Steppe Long Term Ecological Research site located in northeastern Colorado. For eight years, we applied sawdust, sugar, industrial lignin, sawdust + sugar, and lignin + sugar to plots...

[1] Most global ecosystem models assume that controls over soil organic matter are alike in climatically similar regions. In this study, we tested the generality of controls over soil organic carbon (SOC) and soil organic nitrogen (SON) in temperate grasslands. We measured organic matter pools in Inner Mongolia, China, along the Northeast China Tra...

Active crown fires affect forest ecosystem structure and function, and the livelihood of the surrounding human communities. Researchers and managers use simulation models to understand fire behavior and predict fire hazard. Accurate predictions depend on the capacity of simulation models to represent the processes that control fire behavior and on...

Plants reflect resource use in their spatial patterning. Competition for limited resources—such as available soil water in a dryland ecosystem—drives establishment, growth, and mortality, resulting in shifts of spatial arrangement over time. We characterized the spatial patterning of two big sagebrush (Artemisia tridentata subspecies wyomingensis)...

Livestock grazing is a globally important land‐use and has the potential to significantly influence plant community structure and ecosystem function, yet several critical knowledge gaps remain on the direction and magnitude of grazing impacts. Furthermore, much of our understanding of the long‐term effects on plant community composition and structu...

Estimating plant biomass in rangeland ecosystems is essential to understanding carbon cycling, impacts on natural resources, and ecological functioning or structure—all of which inform sustainable land management. However, biomass estimation has been relatively understudied for the sagebrush steppe of North America, one of the continent's most wide...

The Systems Ecology Paradigm (SEP) incorporates humans as integral parts of ecosystems and emphasizes issues that have significant societal relevance such as grazing land, forestland, and agricultural ecosystem management, biodiversity and global change impacts. Accomplishing this societally relevant research requires cutting-edge basic and applied...

Root production is known to contribute at least 50% of total net primary production in dryland ecosystems, yet few studies have addressed seasonal dynamics of root production or the belowground response to altered resource availability. We aimed to identify how root production varies across three dryland ecosystems dominated by different plant func...

Soil moisture, and hence precipitation, exerts a dominant control on net primary productivity (NPP; the rate of carbon accumulation by autotrophs) in semiarid to subhumid ecosystems, such as grasslands and shrublands. At the global scale, mean annual precipitation has been shown to account for >50% of the variance in aboveground net primary product...

The probability of extreme weather events is increasing, with the potential for widespread impacts to plants, plant communities, and ecosystems. Reports of drought‐related tree mortality are becoming more frequent along with increasing evidence that drought accompanied by high temperatures is especially detrimental. Simultaneously, extreme large pr...

In drylands, the coexistence of grasses and woody plants has been attributed to soil water resource partitioning. Soil texture and precipitation seasonality can influence the amount and distribution of water in the soil, and their interaction may play an important role in determining the relative importance of grasses and woody plants. We investiga...

Nitrogen additions are known to elicit variable responses in semi-arid ecosystems, with responses increasing with precipitation. The response of semi-arid ecosystems to nitrogen are important to understand due to their large spatial extent worldwide and the global trend of increasingly available nitrogen. In this study, we evaluated the impact of a...

Dryland soils store approximately 10-15% of the world's soil organic matter (SOM) to 1 m. Threats to carbon stocks in global dryland soils include cultivation, overgrazing, urbanization, and energy development. To limit loss of carbon from these soils, it is important to understand, first, how disturbances affect SOM and second, how SOM recovers af...

Nitrogen additions are known to elicit variable responses in semi-arid ecosystems, with responses increasing with precipitation. The response of semi-arid ecosystems to nitrogen are important to understand due to their large spatial extent worldwide and the global trend of increasingly available nitrogen. In this study, we evaluated the impact of n...

Reclamation is an application of treatment(s) following disturbance to promote succession and accelerate the return of target conditions. Previous studies have framed reclamation in the context of succession by studying its effectiveness in reestablishing late-successional plant communities. Reestablishment of plant communities is especially import...

The potential influence of seed bank composition on range shifts of species due to climate change is unclear. Seed banks can provide a means of both species persistence in an area and local range expansion in the case of increasing habitat suitability, as may occur under future climate change. However, a mismatch between the seed bank and the estab...

Background/Question/Methods Plants species can respond to climate change by shifting distributions into new suitable habitat, but plants can only “migrate” into new areas through propagation. Long distance seed dispersal is an important mechanism that enables a plant species to track the fast pace of predicted climate change. Upon seed arrival, con...

Oil and natural gas extraction is rapidly expanding in semiarid intermountain big sagebrush ecosystems of the western USA. Formerly covering over 60 million ha, this ecosystem has lost almost half its area due to land use changes. In this study, we measured the natural recovery of the big sagebrush plant community across a chronosequence of 29 oil...

Intensive natural gas development causes habitat loss that reduces nutritional carrying capacity for ungulates and other species of conservation concern. To offset habitat loss from energy development, wildlife managers are experimenting with large-scale sagebrush fertilization on western public rangelands. We synthesize what is known about basic s...

Terrestrial vegetation influences hydrologic cycling. In water‐limited, dryland ecosystems, altered ecohydrology as a consequence of vegetation change can impact vegetation structure, ecological functioning and ecosystem services. Shrub steppe ecosystems dominated by big sagebrush ( A rtemisia tridentata ) are widespread across western N orth A mer...

As the world's population increases, marginal lands such as drylands are likely to become more important for food production. One proven strategy for improving crop production in drylands involves shifting from conventional tillage to no-till to increase water use efficiency, especially when this shift is coupled with more intensive crop rotations....

Across US Great Plains grasslands, a gradient of increasing mean annual precipitation from west to east corresponds to increasing aboveground net primary productivity (ANPP) and increasing N-limitation. Previous work has shown that there is no increase in net N mineralization rates across this gradient, leading to the question of where eastern prai...

Background/Question/Methods The magnitude and frequency of drought is expected to increase in the US Great Plains under future climate regimes. Although semiarid systems are considered resistant to water limitation, the ability of these systems to recover after extended periods of intense drought has not been tested. The objective of our research...

Both biogeographical and rainfall manipulation studies show that soil water content can be a strong driver of microbial community composition. However, we do not yet know if these patterns emerge because certain bacterial taxa are better able to survive at dry soil moisture regimes or if they are due to other drought-sensitive ecosystem properties...

We addressed the rarely studied issue of how different soil organic matter pools respond to disturbances from historical oil and gas well development in semi-arid Intermountain sagebrush steppe. We selected twenty-nine study well sites in south-central Wyoming that were plugged and abandoned 3390 years ago. We designed our study to understand the l...

Increases in wildfire activity in the western United States have prompted land managers to re-evaluate management practices. In the Colorado Front Range, where population density is high, there is often a great concern regarding wildfire which leads to efforts that will reduce fire hazard. The most common method of achieving this goal is to thin th...

Background/Question/Methods Nitrogen (N) loss via gaseous emissions, erosion, and leaching from fields and pastures is a widely recognized environmental problem for modern agriculture. The mechanisms and consequences of N loss are well studied in humid and sub-humid agricultural regions, but less so in semi-arid regions, where leaching is a rare...

Background/Question/Methods The distribution of 15N in soil reflects the sources, sinks, and fractionation processes associated with biotic and abiotic functions. Soil 15N signatures tend to increase with depth, while plant 15N is more variable. As climate change, management, and environmental factors impact the distribution of ecosystems, plants...

In a 10-year study, we assessed the influence of five carbon (C) treatments on the labile C and nitrogen (N) pools of historically N-enriched plots on the Shortgrass Steppe Long Term Ecological Research site located in northeastern Colorado. For eight years, we applied sawdust, sugar, industrial lignin, sawdust + sugar, and lignin + sugar to plots...

Biological activity and the physical environment regulate greenhouse gas fluxes (CH4, N2O and NO) from upland soils. Wildfires are known to alter these factors such that we collected daily weather records, fire return intervals, or specific fire years, and soil data of four specific sites along the Colorado Front Range. These data were used as prim...

The frequency and magnitude of drought is expected to increase in the US Great Plains under future climate regimes. Although semiarid systems are considered highly resistant to water limitation, novel drought events could alter linkages among biogeochemical processes, and result in new feedbacks that influence the timescale of ecosystem recovery. W...

Background/Question/Methods Central US grassland communities vary across a longitudinal precipitation gradient from semiarid shortgrass steppe in the western portion, through the central mixed-grass prairie, to the sub-humid tallgrass prairie in the east. There are strong interactions among water availability, nitrogen (N) dynamics and plant comm...

Background/Question/Methods Semi-arid sagebrush steppe areas of the western U. S. are experiencing intense increases in oil and gas development over the past few decades. Reclamation of oil and gas wells requires knowledge about the long term patterns of natural recovery in this system. Our research addresses the pattern of community and soil org...

Biological activity and the physical environment regulate greenhouse gas fluxes (CH₄, N₂O and NO) from upland soils. Wildfires are known to alter these factors such that we collected daily weather records, fire return intervals, or specific fire years, and soil data of four specific sites along the Colorado Front Range. These...

Cropping practices in the Great Plains of the U.S. have led to large losses in soil organic carbon (SOC) and nitrogen (N). Land converted to perennial vegetation through the Conservation Reserve Program (CRP) has the potential to recover these losses and sequester anthropogenic carbon. We studied 18 years of SOC and N recovery in CRP fields seeded...

1. Models predict that the duration and intensity of drought will increase under future climate regimes. Although semi-arid grasslands are adapted to moisture limitation, the sensitivity of semi-arid grassland vegetation to extreme and sustained dry periods that may occur in the future has not been tested. 2. In this study, we analysed vegetation c...

Background/Question/Methods Wildfires in the Colorado montane forest burned with no anthropogenic suppression for millennia leading up to European settlement beginning in the late 19th century. In this study I examine the period between 1700-1900 (“pre-European”). Fires have been successfully suppressed during recent decades (~1950-2010) in this r...

Background/Question/Methods Drought is likely to become more frequent and more severe under future climate regimes. Despite microorganisms’ important role in ecosystem function and our extensive knowledge of community responses to disturbance in plant systems, we do not know how microbial communities will respond to extreme moisture events, and w...

Nitrogen (N) and water additions in the shortgrass steppe change the dominance of plant functional types (PFT) that are characterized by different photosynthetic pathways and phenologies. We aimed to examine monthly patterns of plant N and microbial N storage during the growing season, and to assess whether N fertilization last applied 30years ago...

Wildfires affect Rocky Mountain ecosystems across a wide range of spatial and temporal scales. Many of the resulting changes are greatest for environmental factors, such as substrate and microclimate that control exchanges of greenhouse gases. We investigated this link to understand how time since fire influences the cycling of these gases through...

I recently returned from the annual meeting of the Ecological Society of America (ESA), my principal scientific society. This year's conference theme was “Global Warming: The legacy of our past, the challenge for our future.” Roughly 4000 scientists attended from countries around the world to

In water-limited ecosystems, small rainfall events can have dramatic impacts on microbial activity and soil nutrient pools. Plant community phenology and life span also affect soil resources by determining the timing and quantity of plant nutrient uptake, storage, and release. Using the replacement of C3–C4 perennial grasses by the invasive annual...

Background/Question/Methods Recent climate change predictions suggest an increase in the spatial extent of land subjected to wildfire in the western U.S. Forest fires can result in an immediate release of carbon to the atmosphere, compared to the gradual storage of carbon in forests over decades as they grow and mature. Due to a heightened interest...

Pulses of water availability characterize semiarid and arid ecosystems. Most precipitation events in these ecosystems are small (≤10mm), but can stimulate carbon flux. The large proportion of carbon stored belowground and small carbon inputs create the potential for these small precipitation events to have large effects on carbon cycling. Land-use...

Late last year, a prototype Flash LIDAR instrument flew on a series of airborne tests to demonstrate its potential for improved vegetation measurements. The prototype is a precursor to the Electronically Steerable Flash LIDAR (ESFL) currently under development at Ball Aerospace and Technology Corp. with funding from the NASA Earth Science Technolog...

One of the major concerns about global warming is the potential for an increase in decomposition and soil respiration rates, increasing CO2 emissions and creating a positive feedback between global warming and soil respiration. This is particularly important in ecosystems with large belowground biomass, such as grasslands where over 90% of the carb...

Background/Question/Methods Climate models predict that precipitation patterns will change in the coming decades, and in the U.S. Great Plains, the frequency and duration of summer droughts is predicted to increase. Because water is the most frequently limiting resource in semi-arid systems, increased drought will have significant effects on ecosy...

Background/Question/Methods Semiarid ecosystems are particularly interesting with respect to biogeochemical cycling; the key abiotic variables controlling biogeochemical pools and processes (carbon and nitrogen storage, NPP, and nutrient exchange dynamics) are water availability and temperature, as they vary in time and space, and soil texture as i...

10.1111/j.1365-2486.2009.02086.x

Decomposition is a critical process in global carbon cycling. During decomposition, leaf and fine root litter may undergo a later, relatively slow phase; past long-term experiments indicate this phase occurs, but whether it is a general phenomenon has not been examined. Data from Long-term Intersite Decomposition Experiment Team, representing 27 si...

We assessed the influence of annual and seasonal climate variability over soil organic matter (SOM), above-ground net primary production (ANPP) and in situ net nitrogen (N) mineralization in a regional field study across the International Geosphere Biosphere Programme (IGBP) North American mid-latitude transect (Koch et al. 1995). We hypothesized t...

Recognition of the importance of land-use history and its legacies in most ecological systems has been a major factor driving the recent focus on human activity as a legitimate and essential subject of environmental science. Ecologists, conservationists, and natural resource policymakers now recognize that the legacies of land-use activities contin...

Human activities affect the natural environment at local to global scales. To understand these effects, knowledge derived from short-term studies on small plots needs to be projected to much broader spatial and temporal scales. One way to project short-term, plot-scale knowledge to broader scales is to embed that knowledge in a mechanistic model of...

Many studies have analyzed the benefits, costs, and carbon storage capacity associated with urban trees. These studies have been limited by a lack of research on urban tree biomass, such that estimates of carbon storage in urban systems have relied upon allometric relationships developed in traditional forests. As urbanization increases globally, i...

Regional analyses and biogeochemical models predict that ecosystem N pools and N cycling rates must increase from the semi-arid shortgrass steppe to the sub-humid tallgrass prairie of the Central Great Plains, yet few field data exist to evaluate these predictions. In this paper, we measured rates of net N mineralization, N in above- and belowgroun...

As atmospheric CO2 increases, ecosystem carbon sequestration will largely depend on how global changes in climate will alter the balance between net primary production and decomposition. The response of primary production to climatic change has been examined using well-validated mechanistic models, but the same is not true for decomposition, a prim...

Ecology of the Shortgrass Steppe: A Long-Term Perspective summarizes and synthesizes more than sixty years of research that has been conducted throughout the shortgrass region in North America. The shortgrass steppe was an important focus of the International Biological Program's Grassland Biome project, which ran from the late 1960s until the mid-...

Where lies the future of the shortgrass steppe? In prior chapters we have described the remarkable resilience of the shortgrass steppe ecosystem and its organisms to past drought and grazing, and their sensitivity to other types of change. Emerging from this analysis is the idea of vulnerability to two main forces: future changes in precipitation o...

The central grassland region of North America (Fig. 1.1) is the largest contiguous grassland environment on earth. Prior to European settlement, it was a vast, treeless area characterized by dense head-high grasses in the wet eastern portion, and very short sparse grasses in the dry west. As settlers swept across the area, they replaced native gras...

Net primary production (NPP), the amount of carbon or energy fixed by green plants in excess of their respiratory needs, is the fundamental quantity upon which all heterotrophs and the ecosystem processes they are associated with depend. Understanding NPP is therefore a prerequisite to understanding ecosystem dynamics. Our objectives for this chapt...

Background/Question/Methods Our synthesis proposes that there are three key propositions of ecosystem ecology. In these, we seek to integrate ecosystem ecology and biogeochemistry, evolutionary ecology of organisms, and human impacts on ecosystems. Results/Conclusions First, ecosystems are constrained by the laws of thermodynamics, but becaus...

Ecological modeling has played a key role in scientific investigations of the SGS LTER during the past several decades. The SGS LTER site, focused initially on the Central Plains Experimental Range (CPER), was the main grassland research site for the Grassland Biome component of the U.S. IBP effort (Lauenroth et al., this volume, chapter 1). Initia...

Since the days of the IBP, there has been a strong emphasis on research about the biogeochemistry of shortgrass steppe ecosystems (e.g., Clark, 1977; Woodmansee, 1978). A major theme has been seeking to understand spatial and temporal patterns and controls of biogeochemical pools and fluxes at scales that span from several centimeters to hundreds o...

This synthetic data set contains plant species relative abundance measures from 35 nitrogen (N) fertilization experiments conducted at 10 sites across North America. The data set encompasses the fertilization responses of 575 taxa from 1159 experimental plots. The methodology varied among experiments, in particular with regard to the type and amoun...

The positive effect of disturbance on plant community invasibility is one of the more consistent results in invasion ecology. It is generally attributed to a coincident increase in available resources (due to the disturbance) that allows non-resident plant species to establish (Davis MA, Grime JP Thompson K, J Ecol 88:528–534, 2000). However, most...

Restoring the natural fire regime to forested systems that have experienced fire exclusion throughout the past century can be a challenge due to the heavy fuel loading conditions. Fire is being re-introduced to mixed conifer forests in the Sierra Nevada through both early season and late season prescribed burns, even though most fires historically...

We investigated soil CO 2 fl ux and bare soil respiration in grasslands that are located at the southern edge of the Siberian boreal forest in Northern Mongolia. The study area has warmed by almost 1.8 o C over the last 40 years, and the soil and vegetation covers have been changed due to intense nomadic grazing pressure. Bare soil respiration is d...

W here lies the future of the shortgrass steppe? In prior chapters we have described the remarkable resilience of the shortgrass steppe ecosystem and its organisms to past drought and grazing, and their sensitivity to other types of change. Emerging from this analysis is the idea of vulnerability to two main forces: future changes in precipitation...